US5772728A - Method for upgrading of silicon-containing residues obtained after leaching of copper-containing residues from chlorosilane synthesis - Google Patents

Method for upgrading of silicon-containing residues obtained after leaching of copper-containing residues from chlorosilane synthesis Download PDF

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US5772728A
US5772728A US08/859,819 US85981997A US5772728A US 5772728 A US5772728 A US 5772728A US 85981997 A US85981997 A US 85981997A US 5772728 A US5772728 A US 5772728A
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residue
slag
silicon
copper
smelting furnace
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US08/859,819
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Inger Johanne Eikeland
Roald Gundersen
Ragnhild Jensen
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Elkem ASA
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Elkem ASA
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/037—Purification
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/12—Organo silicon halides
    • C07F7/16—Preparation thereof from silicon and halogenated hydrocarbons direct synthesis

Definitions

  • the present invention relates to a method for upgrading residues from methylchlorosilane synthesis, where silicon is reacted with methylchloride in the presence of a copper catalyst and residues from chlorosilanesynthesis, where silicon is reacted with hydrogenchloride.
  • Methylchlorosilane synthesis is carried out in fluidized bed reactors.
  • a part of fine particulate silicon and copper catalyst particles are together with metallic compounds, especially iron- and aluminium compounds, which are present in the silicon raw material, removed from the reactor together with the gaseous reaction products, a mixture of silanes, and unreacted methylchloride.
  • the solid materials are separated from the mixture of silanes and unreacted methylchloride in separating devices such as for example cyclones.
  • a residue will remain in the reactor, comprising silicon, copper and metal halides formed from compounds in the silicon raw materials and also comprising carbon deposits formed by decomposition of methylchloride. This residue is continuously or intermittently removed from the reactor.
  • Elemental copper, copper oxides, copper formate, copper hydroxides and other copper salts like copper chloride are used as a copper catalyst.
  • the copper catalyst may further contain metals or metal compounds as activators, such as zinc, and zinc compounds, or promotors such as antimony, cadmium, phosphorus, tin, arsenic etc. in order to improve the reactivity and the selectivity of the produced silanes.
  • DE-A 4205980 it is proposed to treat residue from direct synthesis by diluted sulphuric acid at elevated temperatures in order to dissolve copper and where copper can be precipitated as for example cuprous chloride or as copper-II-oxalat or where copper can be recovered by electrolysis. It is further disclosed in DE-A 4205980 that it is obtained a solid silicon residue which can be used in metallurgical processes or which can be deposited. Chemical analysis of the obtained silicon residue is, however, not given.
  • an inert slag it is understood a material which satisfies the requirements set to an inert material in Review of Regulatory Situation on Waste at EC and OECD levels, published February 1993.
  • the present invention relates to a method for upgrading silicon-containing solid residues obtained after leaching of copper from copper-containing residues from direct synthesis of organochlorosilanes, said method being characterized in that the solid residue, optionally together with an oxidation agent, is supplied to a smelting furnace where the residues are melted and form a molten metallic phase substantially containing silicon and a calcium silicate slag and tapping of the molten metallic phase and an inert slag from the smelting furnace.
  • the residues are dried and agglomerated before they are supplied to the smelting furnace.
  • the agglomeration is carried out by conventional methods such as for example pelletizing using a suitable binder.
  • the residues can be supplied to the smelting furnace in powder form by injection through a hollow electrode or by injection through a lance or through nozzles arranged in the furnace bottom or in the furnace body.
  • the residues can either be in powder form or agglomerated form.
  • CaO, SiO 2 or Al 2 O 3 are added as slag forming materials in order to produce a calcium silicate or a calcium aluminate silicate slag which is liquid at the temperature in the smelting furnace and is inert after solidification.
  • the basicity of the slag defined for example as weight ratio CaO/SiO 2 is preferably adjusted within the range of 0.5 to 3.0.
  • the smelting process may be carried out in plasma heated furnaces or in furnaces equipped with graphite- or carbon electrodes.
  • the current supply can be direct current or alternate current. Both open, semi-closed or closed smelting furnaces can be used.
  • the use of a closed smelting furnace gives, however, the best control of gas production. This may be an advantage as to the amount of gas and to avoid outlet of dioxine to the environment.
  • oxidizing agent a metal oxide or an oxygen containing gas can be used.
  • the purpose of the supply of an oxidation agent is to oxidize any elemental carbon present in the residue.
  • an iron oxide source is added as oxidation agent to the smelting furnace in an amount sufficient to oxidize elemental carbon present in the residue.
  • the molten metallic phase will, in addition to silicon and copper, contain iron which during the solidification of the metallic phase will form a FeSi 2 intermetallic phase.
  • amorphous silica dust will be formed which will follow the off gas from the furnace.
  • This silica dust can be recovered from the off gas in for example a bag house filter and can be used as a binder for producing agglomerates of the residue or it can be used as an additive in the production of concrete and mortar.
  • the gas can be cleaned by wet cleaning, whereby the amorphous silica can be recovered in the form of a liquid slurry.
  • silicon or a silicon-iron alloy is obtained which can be used as an additive in the production of steel or cast iron or as a reduction agent in silicothermic production of metals or metal alloys.
  • the inert slag can be used as a filler material or it can be deposited.
  • a solid residue obtained after leaching of copper from a copper-containing residue for organochlorosynthesis was agglomerated using a binder which, based on the weight of the agglomerates, consisted of 2% by weight of amorphous silica fume, 3% by weight of slaked lime, 2% by weight of an aqueous sugar solution and water in an amount of up to 17% by weight.
  • Agglomerates having a composition as shown in Table 1 were melted in a smelting furnace equipped with a plasma burner.
  • a start melt was established in the furnace comprising silicon and a slag consisting of about 55% by weight of CaO and about 45% by weight of SiO 2 .
  • the solid residue was together with CaO and SiO 2 as slagforming material and Fe 2 O 3 as oxidation agent supplied to the slag bath.
  • the purpose of the addition of Fe 2 O 3 was to consume free carbon in the solid residue by reduction of Fe 2 O 3 to Fe.
  • the silicon-iron alloy can for example be used as an additive in steel and cast iron production or as a reduction agent in silicothermic production of metals and metal alloys.
  • the off-gas from the smelting furnace was cleaned in a wet cleaning apparatus. From the wet cleaning apparatus a sludge consisting essentially of SiO 2 was recovered.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)

Abstract

The present invention relates to a method for upgrading silicon-containing solid residues obtained after leaching of copper from copper-containing residues from direct synthesis of organochlorosilanes. Solid residue, optionally together with an oxidation agent, is supplied to a smelting furnace where the residues are melted and form a molten metallic phase substantially containing silicon and a calcium silicate slag and tapping of the molten metallic phase and an inert slag from the smelting furnace.

Description

This application is a continuation of application Ser. No. 08/537,934 filed Oct. 26, 1995 now abandoned.
TECHNICAL FIELD
The present invention relates to a method for upgrading residues from methylchlorosilane synthesis, where silicon is reacted with methylchloride in the presence of a copper catalyst and residues from chlorosilanesynthesis, where silicon is reacted with hydrogenchloride.
BACKGROUND ART
Methylchlorosilane synthesis, also called direct synthesis, is carried out in fluidized bed reactors. During the process a part of fine particulate silicon and copper catalyst particles are together with metallic compounds, especially iron- and aluminium compounds, which are present in the silicon raw material, removed from the reactor together with the gaseous reaction products, a mixture of silanes, and unreacted methylchloride. The solid materials are separated from the mixture of silanes and unreacted methylchloride in separating devices such as for example cyclones. In addition a residue will remain in the reactor, comprising silicon, copper and metal halides formed from compounds in the silicon raw materials and also comprising carbon deposits formed by decomposition of methylchloride. This residue is continuously or intermittently removed from the reactor.
Elemental copper, copper oxides, copper formate, copper hydroxides and other copper salts like copper chloride are used as a copper catalyst. The copper catalyst may further contain metals or metal compounds as activators, such as zinc, and zinc compounds, or promotors such as antimony, cadmium, phosphorus, tin, arsenic etc. in order to improve the reactivity and the selectivity of the produced silanes.
These residues have up till now normally been deposited on waste disposal sites. However, as the residues normally contain 1-10% by weight of copper, mainly in elemental form, copper may be leached from the residue which represents a danger for pollution of ground water. It is therefore no longer acceptable to deposit this type of residue on disposal sites.
A number of methods for recovering copper from the above mentioned residues have been proposed. Thus from German patent No. 901889 it is known to treat residue from the reactor in water and diluted hydrochloric acid under addition of chlorine gas in order to leach copper as divalent copper chloride and remove the remaining solid residue from the solution whereafter divalent copper chloride in the leach solution is reduced to cuprous chloride which is crystallized and used as a copper catalyst in the direct synthesis. The remaining solid residue, which mainly contains silicon must, however, be deposited. In addition it is difficult to obtain a complete crystallization of cuprous chloride from the leach solution, making it necessary to subject the final solution to further treatment.
From DE-A1 3523541 it is known a method for treatment of a hydrolysis residue from organochlorosilane production, where the residue is oxidized by sodium hypochlorite in order to leach copper from the residue. After removal of the solids from the leach solution, an alkaline earth- or alkaline hydroxide or an alkaline carbonate are added in order to precipitate copper oxides, hydroxides or carbonates. Also in this process the undissolved solid material which mainly contains silicon, is deposited.
In U.S. Pat. No. 4,758,352 it is proposed to oxidize hydrolysis residue by using an oxygen containing gas. Also in this process only copper is recovered, while a silicon containing residue is deposited.
In DE-A 4205980 it is proposed to treat residue from direct synthesis by diluted sulphuric acid at elevated temperatures in order to dissolve copper and where copper can be precipitated as for example cuprous chloride or as copper-II-oxalat or where copper can be recovered by electrolysis. It is further disclosed in DE-A 4205980 that it is obtained a solid silicon residue which can be used in metallurgical processes or which can be deposited. Chemical analysis of the obtained silicon residue is, however, not given.
By all the above-mentioned processes the residues are subjected to a leaching process in order to dissolve and recover copper while the undissolved solid matter is normally deposited. This undissolved matter does, however, contain a substantial amount of silicon which is not recovered.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a method for upgrading silicon-containing solid residues obtained after leaching of copper from copper-containing residues from direct synthesis of organochlorosilanes, whereby a silicon-containing product can be recovered and whereby an inert slag can be produced and can be used as a filler material and can be deposited without restrictions. By an inert slag it is understood a material which satisfies the requirements set to an inert material in Review of Regulatory Situation on Waste at EC and OECD levels, published February 1993.
Accordingly, the present invention relates to a method for upgrading silicon-containing solid residues obtained after leaching of copper from copper-containing residues from direct synthesis of organochlorosilanes, said method being characterized in that the solid residue, optionally together with an oxidation agent, is supplied to a smelting furnace where the residues are melted and form a molten metallic phase substantially containing silicon and a calcium silicate slag and tapping of the molten metallic phase and an inert slag from the smelting furnace.
According to a preferred embodiment the residues are dried and agglomerated before they are supplied to the smelting furnace. The agglomeration is carried out by conventional methods such as for example pelletizing using a suitable binder. Alternatively the residues can be supplied to the smelting furnace in powder form by injection through a hollow electrode or by injection through a lance or through nozzles arranged in the furnace bottom or in the furnace body. When the residues are supplied through a hollow electrode or injected through lances or nozzles directly into the molten bath, the residues can either be in powder form or agglomerated form.
If necessary CaO, SiO2 or Al2 O3 are added as slag forming materials in order to produce a calcium silicate or a calcium aluminate silicate slag which is liquid at the temperature in the smelting furnace and is inert after solidification. The basicity of the slag defined for example as weight ratio CaO/SiO2 is preferably adjusted within the range of 0.5 to 3.0.
The smelting process may be carried out in plasma heated furnaces or in furnaces equipped with graphite- or carbon electrodes. The current supply can be direct current or alternate current. Both open, semi-closed or closed smelting furnaces can be used. The use of a closed smelting furnace gives, however, the best control of gas production. This may be an advantage as to the amount of gas and to avoid outlet of dioxine to the environment.
As the oxidizing agent a metal oxide or an oxygen containing gas can be used. The purpose of the supply of an oxidation agent is to oxidize any elemental carbon present in the residue.
According to a preferred embodiment, an iron oxide source is added as oxidation agent to the smelting furnace in an amount sufficient to oxidize elemental carbon present in the residue. In this case the molten metallic phase will, in addition to silicon and copper, contain iron which during the solidification of the metallic phase will form a FeSi2 intermetallic phase.
During the smelting of the residue some amorphous silica dust will be formed which will follow the off gas from the furnace. This silica dust can be recovered from the off gas in for example a bag house filter and can be used as a binder for producing agglomerates of the residue or it can be used as an additive in the production of concrete and mortar. Alternatively the gas can be cleaned by wet cleaning, whereby the amorphous silica can be recovered in the form of a liquid slurry.
By the method according to the present invention silicon or a silicon-iron alloy is obtained which can be used as an additive in the production of steel or cast iron or as a reduction agent in silicothermic production of metals or metal alloys. The inert slag can be used as a filler material or it can be deposited.
EXAMPLE
A solid residue obtained after leaching of copper from a copper-containing residue for organochlorosynthesis was agglomerated using a binder which, based on the weight of the agglomerates, consisted of 2% by weight of amorphous silica fume, 3% by weight of slaked lime, 2% by weight of an aqueous sugar solution and water in an amount of up to 17% by weight. Agglomerates having a composition as shown in Table 1 were melted in a smelting furnace equipped with a plasma burner.
              TABLE 1                                                     
______________________________________                                    
Composition of agglomerated solid residue.                                
       Element                                                            
              Weight %                                                    
______________________________________                                    
       Fe     1.7                                                         
       Zn     0.01                                                        
       Cu     0.3                                                         
       Mn     0.03                                                        
       Cr     0.01                                                        
       Ti     0.13                                                        
       Ca     1.2                                                         
       Al     0.33                                                        
       Mg     0.02                                                        
       C      4.8                                                         
       Cl     1.13                                                        
       Si     78.6                                                        
       Remainder                                                          
              Oxygen                                                      
______________________________________
Before the solid residue was supplied to the smelting furnace, a start melt was established in the furnace comprising silicon and a slag consisting of about 55% by weight of CaO and about 45% by weight of SiO2.
The solid residue was together with CaO and SiO2 as slagforming material and Fe2 O3 as oxidation agent supplied to the slag bath. The purpose of the addition of Fe2 O3 was to consume free carbon in the solid residue by reduction of Fe2 O3 to Fe.
From the smelting furnace a silicon-iron alloy and a calcium silicate slag was tapped. The chemical analysis of the produced silicon-iron alloy is shown in Table 2. The silicon-iron alloy can for example be used as an additive in steel and cast iron production or as a reduction agent in silicothermic production of metals and metal alloys.
              TABLE 2                                                     
______________________________________                                    
Composition of Si--Fe (Cu)-alloy.                                         
       Element                                                            
              Weight %                                                    
______________________________________                                    
       Al     0.50                                                        
       Ca     1.4                                                         
       Ti     0.14                                                        
       Fe     9.9                                                         
       Cu     0.4                                                         
       Si     86.0                                                        
       O.sub.2                                                            
              <1.0                                                        
______________________________________
The off-gas from the smelting furnace was cleaned in a wet cleaning apparatus. From the wet cleaning apparatus a sludge consisting essentially of SiO2 was recovered.
The chemical analysis of the solidified calcium aluminate slag is shown in Table 3. This kind of slag fullfills the requirements set to an inert material stated in Review of Regulatory Situation on Waste at EC and OECD levels, published February 1993.
              TABLE 3                                                     
______________________________________                                    
Composition of slag.                                                      
            Weight %                                                      
______________________________________                                    
        CaO   56.4                                                        
        FeO   2.9                                                         
        MgO   <0.01                                                       
        TiO.sub.2                                                         
              0.04                                                        
        MnO   0.03                                                        
        ZnO   0.011                                                       
        PbO   <0.01                                                       
        SiO.sub.2                                                         
              39.5                                                        
        Al.sub.2 O.sub.3                                                  
              1.2                                                         
______________________________________

Claims (8)

We claim:
1. Method for upgrading a silicon and copper containing solid residue to obtain a silicon product comprising the steps of:
obtaining a solid residue from a direct synthesis of organochlorosilanes, said solid residue being a silicon and copper containing waste product from said synthesis;
leaching said residue to extract copper therefrom;
supplying the solid leached residue optionally together with an oxidation agent to a smelting furnace;
melting the residue and optional oxidizing agent to form a melt comprising a molten metallic phase substantially containing silicon and a slag phase comprising a calcium silicate slag; and
tapping the molten metallic phase and said slag phase from the smelting furnace, said slag phase being inert and said molten metallic phase being said silicon product.
2. Method according to claim 1 wherein the residue is dried and agglomerated before the residue is supplied to the furnace.
3. Method according to claim 1 wherein the residue is supplied to the smelting furnace in powder form by injection through a hollow electrode or by injection into the melt by means of a lance or through nozzles arranged in the smelting furnace.
4. Method according to claim 1 wherein at least one slag forming material selected from the group consisting of CaO, SiO2, and Al2 O3 is added to the furnace to produce a liquid slag.
5. Method according to claim 1 wherein said slag has a basicity defined as a weight ratio CaO/SiO2, and said basicity is adjusted within a range of 0.5 to 3.0.
6. Method according to claim 1 wherein said oxidizing agent is a metal oxide or an oxygen-containing gas.
7. Method according to claim 6 wherein said metal oxide is iron oxide.
8. Method according to claim 4 wherein the slag has a basicity defined as a weight ratio CaO/SiO2 and said basicity is adjusted within the range of 0.5 to 3.0.
US08/859,819 1994-03-30 1997-05-19 Method for upgrading of silicon-containing residues obtained after leaching of copper-containing residues from chlorosilane synthesis Expired - Fee Related US5772728A (en)

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NO941174A NO180189C (en) 1994-03-30 1994-03-30 Process for the preparation of silicon-rich, undissolved residues from leaching of copper-containing residues from organochlorosilane synthesis
NO941174 1994-03-30
US53793495A 1995-10-26 1995-10-26
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008025263A1 (en) * 2008-05-27 2009-12-03 Rev Renewable Energy Ventures, Inc. Purification of metallurgical silicon, comprises mixing halide containing the metallurgical silicon, melting the mixture, and sublimating the impurities and removing the impurities from the melt in the form of metal halides
US9327987B2 (en) 2008-08-01 2016-05-03 Spawnt Private S.A.R.L. Process for removing nonmetallic impurities from metallurgical silicon
WO2022073579A1 (en) * 2020-10-05 2022-04-14 Wacker Chemie Ag Process of producing technical silicon from silicon metal-containing material
CN114892004A (en) * 2022-04-19 2022-08-12 浙江特力再生资源股份有限公司 Comprehensive recycling process of copper-containing silicon slag

Citations (11)

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DE901889C (en) * 1952-03-06 1954-01-18 Wacker Chemie Gmbh Process for the work-up of used silicon-containing reaction masses resulting from the organosilane production by the direct process
US3704114A (en) * 1971-03-17 1972-11-28 Union Carbide Corp Process and furnace charge for use in the production of ferrosilicon alloys
US3768998A (en) * 1971-11-22 1973-10-30 J Yonemochi Method of smelting high quality ferrosilicon
DE3201312A1 (en) * 1982-01-18 1983-07-28 Skw Trostberg Ag, 8223 Trostberg METHOD FOR CLEANING SILICON
EP0141125A2 (en) * 1983-08-29 1985-05-15 Wacker-Chemie GmbH Treatment of silicon and ferrosilicon with slag
DE3523541A1 (en) * 1985-07-02 1987-01-15 Bayer Ag Process for working up hydrolysed residues arising in the preparation of organochlorosilanes
US4758352A (en) * 1985-07-02 1988-07-19 Bayer Aktiengesellschaft Process for the treatment of hydrolysis residues from organo chlorosilane synthesis
EP0287934A2 (en) * 1987-04-22 1988-10-26 General Electric Company Deactivation of spent silicon powder
US5174810A (en) * 1992-02-19 1992-12-29 Dow Corning Corporation Ferrosilicon smelting in a direct current furnace
DE4205980A1 (en) * 1992-02-27 1993-09-02 Nuenchritz Chemie Gmbh Processing of chloro-silane synthesis residues - by non-oxidative treatment with sulphuric acid
US5651807A (en) * 1994-03-30 1997-07-29 Elkem A/S Method for treatment of residues from organochlorosilane and/or chlorosilansynthesis

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE901889C (en) * 1952-03-06 1954-01-18 Wacker Chemie Gmbh Process for the work-up of used silicon-containing reaction masses resulting from the organosilane production by the direct process
US3704114A (en) * 1971-03-17 1972-11-28 Union Carbide Corp Process and furnace charge for use in the production of ferrosilicon alloys
US3768998A (en) * 1971-11-22 1973-10-30 J Yonemochi Method of smelting high quality ferrosilicon
DE3201312A1 (en) * 1982-01-18 1983-07-28 Skw Trostberg Ag, 8223 Trostberg METHOD FOR CLEANING SILICON
EP0141125A2 (en) * 1983-08-29 1985-05-15 Wacker-Chemie GmbH Treatment of silicon and ferrosilicon with slag
DE3523541A1 (en) * 1985-07-02 1987-01-15 Bayer Ag Process for working up hydrolysed residues arising in the preparation of organochlorosilanes
US4758352A (en) * 1985-07-02 1988-07-19 Bayer Aktiengesellschaft Process for the treatment of hydrolysis residues from organo chlorosilane synthesis
EP0287934A2 (en) * 1987-04-22 1988-10-26 General Electric Company Deactivation of spent silicon powder
US5174810A (en) * 1992-02-19 1992-12-29 Dow Corning Corporation Ferrosilicon smelting in a direct current furnace
DE4205980A1 (en) * 1992-02-27 1993-09-02 Nuenchritz Chemie Gmbh Processing of chloro-silane synthesis residues - by non-oxidative treatment with sulphuric acid
US5651807A (en) * 1994-03-30 1997-07-29 Elkem A/S Method for treatment of residues from organochlorosilane and/or chlorosilansynthesis

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008025263A1 (en) * 2008-05-27 2009-12-03 Rev Renewable Energy Ventures, Inc. Purification of metallurgical silicon, comprises mixing halide containing the metallurgical silicon, melting the mixture, and sublimating the impurities and removing the impurities from the melt in the form of metal halides
DE102008025263B4 (en) * 2008-05-27 2015-08-06 Spawnt Private S.À.R.L. Process for purifying metallurgical silicon
US9327987B2 (en) 2008-08-01 2016-05-03 Spawnt Private S.A.R.L. Process for removing nonmetallic impurities from metallurgical silicon
WO2022073579A1 (en) * 2020-10-05 2022-04-14 Wacker Chemie Ag Process of producing technical silicon from silicon metal-containing material
CN114892004A (en) * 2022-04-19 2022-08-12 浙江特力再生资源股份有限公司 Comprehensive recycling process of copper-containing silicon slag

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